PROPERTIES OF AN UNUSUAL ISOLATE OF RASPBERRY RINGSPOT VIRUS FROM GRAPEVINE IN GERMANY AND EVIDENCE FOR ITS POSSIBLE TRANSMISSION BY PARALONGIDORUS-MAXIMUS

An isolate of raspberry ringspot nepovirus (RRV-P) commonly found infe cting grapevine in localised areas of the German Palatinate, was serol ogically closely related to, but distinguishable from, the English typ e strain of this virus (RRV-E) which is transmitted by Longidorus macr osoma. However, unlike RRV-E, RRV-P had a restricted herbaceous host r ange and produced symptoms reliably in only two hosts, Chenopodium qui noa and Nicotiana occidentalis-accession 37B: these symptoms were a fa int systemic vein clearing which, on most occasions in C. quinoa, was transient. In in vitro studies with herbaceous plant sap, RRV-P infect ivity was lost after diluting 1/100 - 1/500, after storage at 20-degre es-C for 1-3 days and at 4-degrees-C for 45 days: for similar studies with RRV-E, the values were 1/125 000, and more than 15 days at 20-deg rees-C and 4-degrees-C, respectively. RRV-P was difficult to purify in quantity and in most preparations seemed to sediment as a single comp onent corresponding to 'bottom' component of RRV-E. Purified particles of RRV-P, like those of RRV-E, contained a major polypeptide and two RNA species of M(r) 54 000, 2.6 x 10(6) and 1.6 x 10(6) respectively. There was no evidence from RNA preparations from purified virus partic les or, from analysis of dsRNA from infected plants, that RRV-P contai ned a satellite RNA. The incidence of RRV-P in vineyards was not assoc iated with the presence in soils of Longidorus nematodes, but was asso ciated with the distribution in the Palatinate of Paralongidorus maxim us. Furthermore. results from an experiment in Germany in a vineyard p lanted with healthy grapevines in soil fumigated to destroy nematodes, showed spread of RRV-P into these plants from an adjoining source of infected grapevines and soil infested with P. maximus. In laboratory s tudies, RRV-P was transmitted by P. maximus at a very low level betwee n grapevines (used as the virus source and test plants) but not to, or between, herbaceous hosts.